A digital video recorder system as a system that can compress and store a digital video/audio signal based on a large-capacity storage device and restore and reproduce the compressed and stored digital video/audio signal is, for example, a system that collects a signal by using a digital transmission camera, and transmits the collected signal to processing devices for subsequent processing through transmission devices to compress, store, restore, or reproduce the transmitted signal.
Audio signals or video signals input through the digital transmission camera are sampled by a clock in the transmission camera to be converted into a serial digital interface (SDI) audio signal or an SDI video signal and transmitted to the transmission devices.
FIG. 1a is a diagram illustrating a method for transmitting an audio signal in the related art and FIG. 1b is a diagram illustrating a method for transmitting a video signal in the related art.
As illustrated in FIG. 1a, SDI audio signals collected or detected through a plurality of digital transmission cameras are transmitted to an audio processing device through respective SDI audio receiving devices and respective audio transmitting devices. Meanwhile, as illustrated in FIG. 1b, SDI video signals collected or detected through the plurality of digital transmission cameras are transmitted to a video processing device through respective SDI video receiving devices.
Since a plurality of audio signals or a plurality of video signals input into the audio processing devices or the video processing devices is signals collected or detected by different digital transmission cameras as described above, sampling clocks are different from each other and although the sampling clocks are set to be the same, when the digital transmission cameras are installed in different areas, noise or a predetermined difference is generated during transmitting the signal. Consequently, the audio signals or the video signals are input into the audio processing device or the video processing device in forms of signals which have different sampling clocks from each other, that is, are not synchronized. Therefore, there is a problem in that a lot of connection terminals are required to input the signals which are synchronized in the audio processing device and the video processing device.